Conventionally, pneumatic tires that reduce rolling resistance have been proposed in order to contribute to the fuel economy of vehicles such as hybrid vehicles (HV) and electric vehicles (EV) in particular. In recent years, there is an even higher demand for pneumatic tires to make a higher contribution to the fuel economy of vehicles, as concerns for the environment increase.
Reducing the total width (SW) of a pneumatic tire so that the front projected area (the projected area viewed from the rolling direction of the pneumatic tire) is decreased to reduce the air resistance around the tire is known as a method of reducing the rolling resistance of pneumatic tires (for example, see International Patent Publication No. WO/2011/135774).
However, with the method as described above, the ground contact width is reduced as the total width of the pneumatic tire is reduced, so it is necessary to increase the outer diameter (OD) in order to maintain a certain load capacity. Therefore, the ground contact length of the pneumatic tire becomes comparatively longer.
When the ground contact length of a pneumatic tire increases, there is a possibility of an increase in air column resonance caused by natural vibrations of air within the circumferential grooves excited by vibrations and the like of the tread portion of the pneumatic tire, and, as a result, that the external noise will increase.